### Source : Webster's Revised Unabridged Dictionary (1913)

Constant \Con"stant\, n.
1. (Astron.) A number whose value, when ascertained (as by
observation) and substituted in a general mathematical
formula expressing an astronomical law, completely
determines that law and enables predictions to be made of
its effect in particular cases.
2. (Physics) A number expressing some property or condition
of a substance or of an instrument of precision; as, the
dielectric constant of quartz; the collimation constant of
a transit instrument.
{Aberration constant}, or {Constant of aberration} (Astron.),
a number which by substitution in the general formula for
aberration enables a prediction to be made of the effect
of aberration on a star anywhere situated. Its value is
20[sec].47.
{Constant of integration} (Math.), an undetermined constant
added to every result of integration.
{Gravitation constant} (Physics), the acceleration per unit
of time produced by the attraction of a unit of mass at
unit distance. When this is known the acceleration
produced at any distance can be calculated.
{Solar constant} (Astron.), the quantity of heat received by
the earth from the sun in a unit of time. It is, on the C.
G. S. system, 0.0417 small calories per square centimeter
per second. --Young.